The present invention relates to voltage converters, and in particular, to high efficiency charge pump DC to DC converter circuits and methods.
Electronic systems are powered by voltages and currents. Voltage converters are circuits that receive an input voltage, typically constant, and output a different voltage for use in an electronic system. Such circuits are commonly used when a certain power supply voltage is available (e.g., a battery voltage), but different voltages are required to drive various system electronics.
One example voltage converter is a DC to DC (“DC/DC”) voltage converter. A DC/DC voltage converter receives a constant voltage at one voltage value, rather than a oscillating voltage, and produces another constant voltage at another constant voltage value. One example application of a DC/DC converter is in batter applications. Initially, a battery may produce a certain voltage when it is fully charged. The voltage produced by the battery may be larger than one or more voltages required by one or more system components. Thus, a DC/DC converter may be used to reduce the battery voltage to desired levels. Converters that receive an input voltage and produce an output voltage that is less than the input voltage are commonly referred to as “Buck” converters. As energy in the battery is used, the battery voltage may drop to lower values over time. Thus, over time the voltage produced by the battery may be less than the voltages required by one or more system components. In this case, a DC/DC converter may be used to increase the battery voltage to a desired level. Converters that receive an input voltage and produce an output voltage that is greater than the input voltage are commonly referred to as “Boost” converters.
Common techniques for implementing “Buck” or “Boost” converters include switching power supplies that use external inductors or capacitors. However, such circuits require costly external components and require complex architectures for performing both “Buck” and “Boost” operations. Switched capacitor techniques have been used for “Buck” and “Boost” DC/DC converters, but such circuits also require at least two external capacitors. To reduce costs, it is generally desirable to reduce the number of external components and circuit complexity. It is also desirable to improve the efficiency of such circuits so that power consumption is reduced.
Thus, there is a need for improved voltage converters. The present invention solves these and other problems by providing high efficiency charge pump voltage converter circuits and methods.